------------[ cut here ]------------
WARNING: CPU: 0 PID: 5633 at fs/buffer.c:1173 mark_buffer_dirty+0x2c6/0x440 fs/buffer.c:1173
Modules linked in:
CPU: 0 UID: 0 PID: 5633 Comm: syz.0.16 Not tainted 6.14.0-rc5-syzkaller-00268-g1110ce6a1e34 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:mark_buffer_dirty+0x2c6/0x440 fs/buffer.c:1173
Code: 4c 89 f7 e8 5c a2 db ff 49 8b 3e be 20 00 00 00 5b 41 5c 41 5e 41 5f 5d e9 67 d2 fb ff e8 82 5c 74 ff eb 8b e8 7b 5c 74 ff 90 <0f> 0b 90 e9 82 fd ff ff e8 6d 5c 74 ff 90 0f 0b 90 e9 a9 fd ff ff
RSP: 0018:ffffc900030af328 EFLAGS: 00010293
RAX: ffffffff824d8295 RBX: ffff8880449f3101 RCX: ffff88801ae80000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: ffffffff824d8013 R09: 1ffff1100893e63a
R10: dffffc0000000000 R11: ffffed100893e63b R12: dffffc0000000000
R13: ffff8880449f31d0 R14: ffff8880449f31d0 R15: ffff888031d24d78
FS:  00007f1043cd16c0(0000) GS:ffff88801fc00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f266f41f000 CR3: 0000000058ef8000 CR4: 0000000000352ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 mark_buffer_dirty_inode+0x89/0x300 fs/buffer.c:672
 fat12_ent_put+0x1af/0x2e0 fs/fat/fatent.c:173
 fat_free_clusters+0x4c7/0xf60 fs/fat/fatent.c:597
 fat_add_cluster fs/fat/inode.c:114 [inline]
 __fat_get_block fs/fat/inode.c:154 [inline]
 fat_get_block+0x8ff/0xd00 fs/fat/inode.c:189
 __block_write_begin_int+0x692/0x19a0 fs/buffer.c:2116
 block_write_begin fs/buffer.c:2226 [inline]
 cont_write_begin+0x77f/0xb40 fs/buffer.c:2577
 fat_write_begin+0x76/0x140 fs/fat/inode.c:228
 cont_expand_zero fs/buffer.c:2504 [inline]
 cont_write_begin+0x32b/0xb40 fs/buffer.c:2567
 fat_write_begin+0x76/0x140 fs/fat/inode.c:228
 generic_cont_expand_simple+0x18f/0x2b0 fs/buffer.c:2468
 fat_cont_expand+0x60/0x1e0 fs/fat/file.c:223
 fat_fallocate+0x23a/0x2f0 fs/fat/file.c:301
 vfs_fallocate+0x623/0x7a0 fs/open.c:338
 ksys_fallocate fs/open.c:362 [inline]
 __do_sys_fallocate fs/open.c:367 [inline]
 __se_sys_fallocate fs/open.c:365 [inline]
 __x64_sys_fallocate+0xbc/0x110 fs/open.c:365
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f1042d8d169
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f1043cd1038 EFLAGS: 00000246 ORIG_RAX: 000000000000011d
RAX: ffffffffffffffda RBX: 00007f1042fa5fa0 RCX: 00007f1042d8d169
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000004
RBP: 00007f1042e0e2a0 R08: 0000000000000000 R09: 0000000000000000
R10: 000000000000c8ab R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f1042fa5fa0 R15: 00007ffc2580ea58
 </TASK>